Recovery of soluble lead salts from insoluble lead compounds



Aug; 31, 1943.

J. J. MULLIGAN RECOVERY OF SOLUBLE LEAD SALTS FROM INSOLUBLE LEAD COMPOUNDS Filed Sept. 14, 1940 Old Eafieg' Lead Plazts Spars Lead 141994495 RAW LEAD Lea fianer Mad Slanted Leia n flaae 2R0 DUCTS GRI NDER Drassev TORAG E Etc-f5 sodium C b ig. LIXIVIATION WATER Sodium. Chloride CHEM OALS TANKS 10% Acetnc Acid. HEAT STEAMCOILS TREATED RAW MATERIAL mo LIQUOR METAL WASHING FOR COARSE SMELT- METALLIOS WATER ING FINES METALLIOS LIQUOR LEACHING AND OTHER CHEMICALS COA RSE MATERIAL W000 ORRUBBER LINED TANKS- WATER AND STEAM ASH LEAHme DISCAR 0s LIQUOR SOLUBLE LEAD ARSENATE FILTER OLNER 'fg LEA o CHROMATE TYPE (JAKE [,1 R LEAD LEAD TUNGSTATE AcETATE) LEAD MOLYBDATE Acznc A010 TANKS FOR RECOVERY pormous AcE'nc Acm INVENTOR ATTORNEY saltsk suitable for the arsenate, chromatejmolybdate, tungstateface I lead peroxide.

' and lead plates and lead battery mudorsediment, by

potassium carbonate,

Pa ented Aug.3l, 1943 REcovEnYoF SOLUBLE LEAD sALrs FaoM INSOLUBLELEADCOMPOUNDS John J.Mulligan, East Chicago, Ind.,assignor to Lillian RrBirkenstein I 1 Application September 14, 1946, Serial No. 356,885 H 0 Claims. (crate-4am This invention relates to a process of ,recovering soluble lead salts from insoluble-lead com- Anobject of this invention is to provide a ,simple and efiective process forproducing lead and irhpurelad bearing materials and compounds such asfleadsulphate, lead oxide, and At the same time, impurities of its salts," sulphuric acid "and are separated from thelead tate, and other compounds ofleadfrominsoluble antimony and barium sulphate salts. I

, A further object is provide a simplemethod for treating lead bearing materials, such as lead sulphate, spent litharge, sweated lead base drosses, old battery lead plates, lead battery'mud resulting drosses from *liquated battery neutralizing portions and converting portionsof to produce a suitable pure mixture of lead compounds from whichis made a commercial solution of various strengths ofjsoluble lead salts and from these salts the many and varied commercialjlead products, such aslead-arsenate, lead chmmate, lead molybdate, lead tungstate, etc. The invention is described,in a preferred em+ bodiment, by the accompanying drawing, in

which is shown a flow. sheet,illustrating the steps manufacture of the Y the raw materials with the aidJof chemicals so as of the process, thefiow sheet being schematic in character,

In a broad or general way, the process comprises two steps of treatment Ifor the insoluble lead materials w e W In the first step," the raw materials are placed in a suitable vessel together-with awater solution oi' a carbonatefonhydroxide of the alkali metal group in such an amount as willneutralize and convert the-lead compounds present in the may,

In addition to the carbonates and hydroxides 0! the alkalimetal group, ammonium carbonate orhydroxlde may be used to neutralize and con-' vert the insoluble lead compounds in the first step of the process. o

If desired, asuitable mixture of any of these ample,such compounds as sodium carbonate, sodium hydroxide and potassium hydroxide may be used.

raw.materials,-particularly such compounds as lead sulphate, to a I compound of lead, which be readily converted by the second. step of.

the treatment to the form of soluble lead salts.

carbonatesor hydroxides maybe used. For ex- After this treatment, the solutionj mayfbe. re,-

, moved from the insoluble residue, which is then ready for the second step, of the treatment.

The second step in general, comprises, the

treatment of the residue from ,the preceding step witha suitable quantityof formic acid or with acetic acid; in the formof a dilute solution. ,A 10% solution of acetic acid is satisiactory for this purpose. If an aceticj acidlsolution is used, it is preferably combined with other suitable chemicals;

The chemical or chemicals which may be used with acetic acid-include any substance :which will act asra reducing agent with respect to the lead peroxide. All reducing agents will effect the reduction of lead peroxide to lead oxide, {but some substances" are not as satisfactory as others, since some reducing agents .cause other reactions ,whichare not desired. Among the pre-' ferred reagents which will cause reduction are formic acid; sodium .nitrite, potassium nitrite and. other alkali metal andalkalineearth salts of nitrous acid, and hydrogen peroxide, and alkali metal and alkaline earth peroxides. Hydrogen chloride (hydrochloric acid) is also a suitable reducing agent, but should be used in a quantity sufficiently small to efiectthe reduction without causing the formation of appreciablerquantities of lead chloride, whichis difliculty "soluble in *water. Instead of hydro,- chloric acidpsodium chloride, chlorides of potassium, lithium, magnesium,and calcium; as

well-as other water soluble chlorides may be usedtwith the acetic acid. The efiectissubstantially thesame, since the chloride 'salts in the presence of acetic acid form hydrochloric acid;

The quantity of sodium chloride used, should be limited the same as that of hydrochloric acid; :These chemicals "are referred to herein as reducing: agents because their action with respect to lead peroxide is that of reduction." In other words, any of these chemicals will cause lead peroxide to be. reduced to lead oxide.

The second step of the treatment serves convertjthe" insoluble lead compounds to soluble lead salts, such as. the acetate. 7 When formic acid is used alone, the final product, is lead formate. 1 The term solubilityfas used;;herein refers to solubility in water or water solutions.

As a specific illustration of the process, and assuming that lead battery plates are to be used as the raw material, I first removethe lugs and then grind the entire battery grids. The ground material is then treated me hot solution (160 F. or higher) of sodium carbonate with asmall while the solution iskept at from 160 to 212,F.

with steam or other means. After about onehalf hour of such stirring of the whole mixture,

pounds containing lead peroxide, the step of treating the compounds with a solution of acetic the mixture is run over a screen to remove large Q5. metal pieces, then the balance with the liquor is H transferred to the washingandleachingtank,

cantation of the liquor from the insoluble residue. After washing, the residue is leached with acetic acid containing sufficient sodium nitrite to make 'thelead peroxide (Pbozy'soluble. Instead of sodium nitrite, sodium chloride or formic acid or hydrogen peroxide or other suitable material y e l i e c The resulting "lead acetate solution is then-run n'iovedelt 'intervals, as necessary, a'nd contains metal and leached washed wood pulp, rubber; etc. (remaining from separators) that might have been present the original battery lead plat'e.

' The metal-is then taken outof *the'tank and is melted into commercial antimonial lead containirl gfiu'suall-y from 90% to 93% lead, dependin onthe proportion of metallic lead contained in the original gridsjtre'ated. At'the same time, as indicated in the flow sheet, the metallic's recovered from thescreens and filter cake areretur'ned fol smelting.

I The recover-yer the'ac'etic aeidportionsgas-in art dica't'edin-the new sheet, is well known int y and is, therefore, not described in detail, 'it being understood that theiecoveredacid is returned as indicated in thejd rawing to 'thewashing and leaching tank-. I I 5 l i 1 The mechanism o'f all of the reactions which take place in the steps 'of'the treatment described 1 herein is not thoroughly understood, and according'n'o theory is advanced therefor. Howeven it hasbeen shown that by following this treatment,

substantially 'all' of the insoluble lead compounds, and particularlyjlead sulphate lead oxide, and lead peroxide, areconyerted'to-soluble compounds such as the acetate. i 1

This application is a continuation inpart of my copending application, Serial 'No. 166,437, filed September 1Z9, 1937, for Recovery of soluble lead salts from impure lead compounds.

Iclair'nt 4 f 1. In a process for treating iiisolublelad comacid and a reagent causing reduction.

2. In a process for treating insoluble lead compounds containing lead peroxide, the step of treating the compounds with a solution of formic acid. f

3. In a process for treating insoluble lead compounds containing lead peroxide, the step of treating the compounds with a solution containing a mixture of acetic acid and'formic acid.

' l. A process for treating insoluble lead com- "pounds containingj lead sulphate and oxides of f Washing of the mixture is accomplished by 1 lead to produce soluble lead salts, comprising treating the compounds by lixiviation with a solutionof a'cornpound of the group consisting "orammbmum and alkali metal carbonates and hydroxides, removing the solution, and treating the residue with a solution of acetic acid and areagent causing reduction.

5.. A process for treating insolubleglead compounds containing lead sulphate andoxides of lead to produce soluble lead salts, comprising treating the compounds by lixiviation. with. a solution of a compound oft-he' group. consisting cit-ammonium and alkaliinetal' carbonates and hydroxides, removing/the solution and treating the residue wither solution of formic-acid.

6 A. process for'treating insoluble lead, compounds. containing lead sulphate; and oxides of lead to. produce soluble lead salts, comprising treating the ,cornpounds by lixiviation with a solution of .a compound of the group consisting of ammonium and alkali metal carbonates and hydroxides, removing the solution, and treating the residue with solutionIof formic-acid and acetic acid, i

'7. A 'process for treating insoluble-lead compounds containing lead sulphate and oxides of lead to produce soluble lead salts, comprising treating the compounds byli'x'iviation with a solution of a vcompound( f the group consisting of ammonium and alkali r'neta'lcarbonates and hydroxides, removing 'the' slolution, an treating he r id w h a Solutionir'iclu din'g aceti acid r ric. acid. l a

'18. A process for treating insoluble lead com 7 pounds containing lead "sulphatean'd oxides of lead to produce solubleflead, salts, comprising treating the" compounds by liXiviatio'n with a solutioh' o f a, com- .oi the groupfconsisting offammonium ari ka li metal carbonates and hydroxides, removing the solution, and treating the residue with a solution of acetic acid and hydrogenperoxide. i I 9. process of recovering from scrap lead, batteryfpla'tes, lead sulphat spent lead lithargejlcad battery mud, andleaddrOSSeS substantially allmetallic fines asjsoluble, lea salts, comprising grinding the material toreduce it to finely divided form, sub} jec'ting the same to 'lixiviation in a not solution an alkali ir'iet alcarbona'te', removing the'solutiori, washing the insoluble residue withwater,

and then treat ng the residue a solution of acetic acid and formic acid;

the character described for 

